Solar synchronized loads for photovoltaic systems

ABSTRACT

An electrical power supply arrangement includes a solar power device that converts sunlight into DC electrical power. A DC load runs on the DC current electrical power. The DC load may be controlled or adjusted to consume a maximum amount of the electrical output of the solar power device. A DC-to-AC converter converts the DC electrical power into AC electrical power. A controller enables the DC-to-AC converter to receive a portion of the DC current electrical power from the solar power device only if all of the DC current electrical power cannot be consumed by the DC load.

RELATED APPLICATIONS

This application is a continuation of and claims the benefit of U.S.non-provisional application Ser. No. 15/010,369, filed Jan. 29, 2016,which is a continuation of and claims the benefit of U.S.non-provisional application Ser. No. 13/489,412, filed Jun. 5, 2012,which claims the benefit of U.S. Provisional Application No. 61/525,483,filed Aug. 19, 2011. The entire contents of each of said prior-filedapplications being incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to solar power, and, more particularly, torunning DC loads by use of solar power.

Description of the Related Art

Current solar photovoltaic (PV) systems for residential and commercialbuildings typically produce direct current (DC) which is inverted toalternating current (AC) using inverters in and connected to an ACcircuit breaker box within or on the building. Such systems suffer frompower intermittency caused when the grid must make up any short termreduction in PV output. Current HVAC systems such as heat pumps oftenutilize AC-to-DC-to-AC, AC motor controls or AC-to-DC power suppliesespecially when the fans or compressors have variable-speed motors.There are a variety of variable-speed motors which could utilize DCinput. Examples are brushless DC motors (BLDC motors) also known aselectronically commutated motors (ECM), as well as variable-frequencydrives (VFD) for AC motors, which may also be configured to use DC asthe input to the VFD.

For example, a Bosch brand geothermal heat pump uses AC-to-DC powersupply to power a variable speed ECM fan motor. For the purposes of thisinvention description, the phrase “DC motor” refers to any motor systemwhere DC is the PV input to the motor or motor controls, even in thecase of a DC input VFD controlling a variable speed AC motor or similar.

It is known to convert all of the DC from PV to AC for use by ACbuilding loads or for export to the utility grid. What is not known inthe conventional art is to adjust DC loads such that the DC loadsconsume a maximum amount of the DC electrical output of the solarpanels, and to convert DC power from solar panels to AC only if all ofthe DC power is not being consumed by a DC load. Moreover, it is notknown to purposefully manage loads, in a variable manner, on the demandside of the meter in concert with the variability of PV power for thepurpose of reduction in or avoidance of power intermittency on the grid.Further, it is not known in the conventional art that the DC load is inthe form of an HVAC system, such as a heat pump with DC input to the DCphase of AC-DC-AC motor controls.

SUMMARY OF THE INVENTION

The invention is directed to an HVAC power supply arrangement in whichthe DC output from a solar array is either directly or through DC/DCconverters connected to the DC circuits of the HVAC equipment. Thevariable-speed DC motor may be controlled or adjusted to consume amaximum amount of the electrical output of the solar panels, increasingconsumption when output is higher, lowering consumption when output islower. An inverter that is either within (motor control circuits forinstance) or separate from the HVAC equipment may operate in abidirectional mode to invert the DC output from the solar array to ACfor the home circuit if the output energy is not being entirely consumedby the variable-speed DC motor. This technique also enables theintegration of a DC power bus within the home or commercial building fordirect coupling to DC appliances and other DC devices.

In one embodiment, the invention comprises an electrical power supplyarrangement including a solar power device that converts sunlight intoDC electrical power. An adjustable DC load runs on the DC currentelectrical power. An electrical output sensing device senses a level ofelectrical output of the solar power device. A controller is coupled toeach of the adjustable DC loads and the electrical output sensingdevice. The controller receives a signal from the electrical outputsensing device, and adjusts the DC load such that the DC loads consumessubstantially all of the electrical output of the solar power device.The adjusting of the DC loads is performed dependent upon the receivedsignal, and depending on which other loads need to receive power. Forexample, it may be determined how much of the available solar- generatedelectricity should be sent to the HVAC systems and how much should besent to other loads, such as a charging station for an Electric Vehicle(EV).

In another embodiment, the invention comprises an electrical powersupply arrangement including a solar power device that converts sunlightinto DC electrical power. A DC load runs on the DC current electricalpower. A DC-to-AC converter converts the DC electrical power into ACelectrical power. A controller enables the DC-to-AC converter to receivea portion of the DC current electrical power from the solar power deviceonly if all of the DC current electrical power cannot be consumed by theDC load.

In yet another embodiment, the invention comprises an electrical powersupply method including converting sunlight into DC electrical power byuse of a solar power device. The DC current electrical power is providedto a plurality of adjustable DC loads. A level of electrical output ofthe solar power device is sensed. Each of the DC loads is adjusted suchthat the DC loads conjointly consume a maximum amount of the electricaloutput of the solar power device. The adjusting of the DC loads isdependent upon the level of electrical output of the solar power device.

In yet another embodiment, the invention comprises an electrical powersupply method including converting sunlight into DC electrical power byuse of a solar power device. The DC current electrical power is providedto an inverter to provide power to an AC load. A level of electricaloutput of the solar power device is sensed. The AC load or series of ACloads are operated in a variable fashion that optimizes the consumptionof the variable PV DC electrical power in a manner which intends toeliminate or reduce AC power demands from the utility grid. Theadjusting of the AC loads is dependent upon the level of electricaloutput of the solar power device.

The invention may eliminate the need to have an inverter between thephotovoltaic (PV) system and the circuit breaker box. Instead, the DCoutput from the solar array may be either directly, or through DC/DCconverters, connected to the DC circuits of the HVAC equipment. Theinverter within the HVAC equipment then may act in a bidirectional modeto invert the DC from the solar array to AC for the home circuit orutility grid, if the output energy is not being entirely consumed by thevariable-speed DC motor or other DC loads in the building. Thistechnique also enables the integration of a DC power bus within the homeor commercial building for direct coupling to DC appliances and other DCdevices. The elimination of the traditional inverter conventionally usedfor solar systems may greatly reduce system cost, reduce electricallosses due to the inversion, and may result in increased systemefficiency at lower cost. The invention may achieve the lower cost,higher efficiency, and higher reliability through simplification of thesystem.

In another embodiment, electrical DC loads (e.g., HVAC systems,appliances, EV chargers, water pumps, etc.) are adjusted in a variablemanner such that the power consumption of the loads corresponds asclosely as possible to the power available from a PV system. Thisadjustment of the DC loads is intended to result in less variation inthe demand on other power sources in the system (e.g., the utility grid,battery, etc.) by the DC loads. In such applications, the PV output isdesigned to provide adequate power to the load without call foradditional power from the utility or storage device. Utility or storagepower is intended to only provide power during evenings or emergencies.This adjustment of the DC loads may also reduce system losses, minimizeutility transformer size, lower system costs, and increase the abilityof the utility grid to support higher penetration levels of renewableenergy. Such application allows the utilities to avoid the added costsof spinning reserves for the purpose of managing the power intermittencycaused by traditional PV system designs.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned and other features and objects of this invention,and the manner of attaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a block diagram of one embodiment of an electrical powersupply arrangement of the present invention.

FIG. 2 is a block diagram of another embodiment of an electrical powersupply arrangement of the present invention.

FIG. 3 is a flow chart of one embodiment of an electrical power supplymethod of the present invention.

FIG. 4 is a block diagram of yet another embodiment of an electricalpower supply arrangement of the present invention.

FIG. 5 is a diagram illustrating communication between DC loadsaccording to another embodiment of an electrical power supply method ofthe present invention.

FIG. 6 is a block diagram of still another embodiment of an electricalpower supply arrangement of the present invention.

Corresponding reference characters indicate corresponding partsthroughout the several views. Although the exemplification set outherein illustrates embodiments of the invention, in several forms, theembodiments disclosed below are not intended to be exhaustive or to beconstrued as limiting the scope of the invention to the precise formsdisclosed.

DESCRIPTION OF THE PRESENT INVENTION

Referring now to the drawings, and particularly to FIG. 1, there isillustrated one embodiment of an electrical power supply arrangement 10of the present invention including a solar PV array 12, and a DC powerbus 14 electrically connecting array 12 to a bidirectional inverter 16of an HVAC system 18 (or DC input to the DC phase in an AC-DC-AC motorcontroller circuit). Inverter 16 may convert DC voltage from array 12 toa DC voltage level that is appropriate for use by HVAC system 18. Array12 may include a DC-to-DC converter which may convert the DC voltageoutput by the solar array to a voltage level suitable for transmissionon bus 14. Inverter 16 may also convert DC voltage from array 12 to anAC voltage that may be used through the remainder of a house 20 withwhich arrangement 10 is associated. Excess AC power that cannot be usedwithin house 20 may be provided to a grid 22 for use outside of house20. In one embodiment, DC voltage from array 12 may be converted to ACvoltage by inverter 16 only if HVAC system 18 (or other variable AC orDC loads) cannot consume all of the DC power from array 12.

By transferring the DC voltage from array 12 directly to HVAC system 18,arrangement 10 may eliminate the need for a separate inverter to convertthe DC voltage from array 12 to AC voltage for transmission and use byboth AC loads and DC loads (after conversion of the AC voltage back toDC voltage). The omission of the separate inverter may reduce electricallosses, reduce cost, and provide improved reliability of the system.Moreover, the invention may provide a high voltage DC power bus 14 whichmay be used by other appliances within the building or EV chargingsystems.

In another embodiment, the bidirectional inverter may simply be a DCdrive or DC motor, and an optional, often smaller, inverter may be addedto the DC bus. The need for an inverter and the size of the inverter maybe determined by the amount of PV energy, if any, that could not beconsumed by the DC loads under certain building circumstances.

In an alternative embodiment (not shown), the DC/DC conversion at PVarray 12 is omitted. That is, the DC voltage may be transmitted on bus14 in the same voltage as produced by the solar cells of array 12.

In another embodiment (FIG. 2), an electrical power supply arrangement100 of the present invention includes a DC load 118 which can beadjusted by a controller 124 to maximize the use of a varying PV outputof a solar array 112. That is, a power meter 126 or a similar device maysense the output power of solar array 112 and communicate the sensedreading to controller 124, as indicated at 128. In turn, controller 124can adjust DC load 118, as indicated at 130, such that load 118 consumessubstantially all of the power that solar array 112 can produce. Thus,no inverter, or a reduced size inverter, may be needed to feed excess PVoutput into the utility grid (not shown). A practical example would beto run air conditioning motors at lower speed for a longer time underthe reduced solar power output of lower light (e.g., cloudy) conditions.This could achieve the same building cooling, while reducing thevariation (intermittency) of power on the grid, which is highlydesirable to the utility companies. Also, by the load(s) using theentire amount of electrical power produced by the solar array, theinvention avoids the energy losses associated with converting the DCpower from the solar array to AC power, transferring the AC power to thegrid, receiving AC power from the grid, and converting the AC power fromthe grid to DC power.

The same principle may apply to systems utilizing battery storage inplace of, or in addition to, solar arrays. In this case, the batterycontroller and/or charge controller could be reduced or eliminated byadjusting the load to consume all of the power output of the battery. Inone embodiment, the battery ensures that a minimum required level ofelectrical power may be provided to the load when the solar array cannotprovide the minimum required level of electrical power. For example, thebattery may power the electronic controller as well as any electronicsoperating in association with the load. For example, a battery may keeplights operating on the load at night so that a user can interact withthe load, even though the solar array cannot provide power to keep theload fully operating until daylight in the morning. The battery may berecharged by the solar array in the event that the solar array producesmore power than is required by the load. In addition, synchronizing theloads to the available solar energy could reduce the amount andfrequency of charging and discharging batteries in the system which mayextend the battery life. Solar Synchronized Loads can also improvebattery life by reducing the intermittency in batterycharging/discharging in the same way as intermittency in utility griddemand is reduced.

An electrical power supply method 300 (FIG. 3) of the invention isdescribed below with reference to FIGS. 4 and 5. In a first step 302,sunlight is converted into DC electrical power by use of a solar powerdevice. For example, electrical power supply arrangement 400 (FIG. 4)includes a solar array 412 which converts sunlight into DC electricalpower.

In a next step 304, the DC current electrical power is provided to aplurality of adjustable DC loads. As shown in the specific embodiment ofFIG. 4, a plurality of DC loads 418 a through 418 n each receives andruns on the DC current electrical power generated by solar array 412.Alternatively, DC loads 418 may be AC loads.

Next, in step 306, a level of electrical output of the solar powerdevice is sensed. For example, a power meter 426 or a similar device maysense the output power of solar array 412 and communicate the sensedreading to controller 424, as indicated at 428.

In step 308, each of the DC loads is adjusted such that the DC loadsconjointly consume a maximum amount of the electrical output of thesolar power device. The adjusting of the DC loads is dependent upon thelevel of electrical output of the solar power device. In the exampleembodiment of FIG. 4, controller 424 can adjust each of DC loads 418a-n, as indicated at 430 a-n, such that loads 418 a-n in combinationconsume substantially all of the power that solar array 412 can produce.Thus, no inverter, or a reduced size inverter, may be needed to feedexcess PV output into the utility grid (not shown). For example, loads418 a-n may represent n number of air conditioning motors each of whichis primarily responsible for cooling a respective section of a building.In an alternative embodiment, loads 41 8 a-n may represent n number ofrefrigeration and/or ice-making motors. Although the various sections ofthe building may be at or below the desired set temperature (e.g., 72degrees F.), AC motors 418 a-n may continue to run during and around thenoon hour when sunlight is most direct and thus the output of solararray 412 is greatest. Thereby, the various sections of the building maybe “overcooled” to a temperature of approximately between 68 and 71degrees F., for example. By virtue of such overcooling, AC motors 41 8a-n may require less electrical power output from solar array 412 in thelate afternoon when sunlight is less direct and the electrical poweroutput capability of solar array 412 is lower. Thus, the building may beefficiently cooled with only small variations in temperature which maynot be noticeable to the inhabitants of the building. Also, thevariation in the amount of power require from the grid may be reduced,which is highly desirable to the utility companies. Further, by theloads using the full amount of electrical power produced by the solararray, the invention avoids the energy losses associated with convertingthe DC power from the solar array to AC power, transferring the AC powerto the grid, receiving AC power from the grid, and converting the ACpower from the grid to DC power.

In a next step 310, a respective portion of the electrical output of thesolar power device to be consumed by each of the loads is determined,possibly by use of an algorithm or a lookup table. For example, if DCloads 418 a-n represent n number of air conditioning motors coolingrespective sections of a building, then each of the sections of thebuilding may be at different actual temperatures, and possibly may havedifferent set temperatures. Thus, controller 424 may adjust airconditioning (or cooling equipment) motors 418 a-n such that each motorconsumes an amount or portion of electrical power that varies with thedifference between the actual temperature and the set temperature of themotor's respective building section. The algorithm or lookup table maytake into account expected thermal conditions in each of the buildingsections in the immediate future (e.g., in the next three hours). Forexample, a section on the west side of the building that is more exposedto sunlight may be expected to heat up more in the next few afternoonhours, and thus the respective air conditioning motor may be adjusted toconsume a greater portion of the electrical power output of solar array412.

Generally, the HVAC equipment may no longer operate in a digital fashionas in all on or all off. Instead, the compressor and blower unit mayoperate at levels consistent with the output of the solar array. Whenthe sun shines strongest, heat loads tend to be highest. The sameprinciple applies to ice-making and refrigeration.

The step 310 of determining a respective portion of the electricaloutput of the solar power device to be consumed by each of the loads mayinclude controlling a rate of change of an aggregate consumption of theelectrical output of the solar power device by the loads such that therate of change does not exceed a threshold rate of change. Thus, theamount of power drawn from solar array 412 may change with a gradualramp up in order to avoid spikes of power being sent to and/or from thegrid. Such spikes may result in inefficiencies and wasted energy. Forexample, controller 424 may adjust loads 418 a-n such that a rate ofchange of power consumption by loads 418 a-n does not exceed a thresholdor maximum level of Watts per second of time. If the load requires moreenergy than can be delivered from the array, a signal may be sent to theutility advising that the load is planning a gradual ramp and anincreased power call from the utility. The timing of the ramp may beadjustable based upon a feedback loop (power availability) from theutility.

Each of the loads may include a respective processor, and the step ofdetermining a respective portion of the electrical output of the solarpower device to be consumed by each of the loads may includecommunication between the processors. For example, as shown in FIG. 5,loads 518 a-e each includes a respective one of processors 532 a-e. Eachof processors 532 a-e may communicate directly with each of the otherones of processors 532 a-e, as indicated by the dashed double-sidedarrows in FIG. 5. The communication between processors 532 a-e may occurwirelessly, or may be carried by same the electrical conductors thatcarry power to loads 518 a-e. In one embodiment, processors 532 a-ecommunicate with each other in order to conjunctively determine how muchpower will be drawn by each of loads 518 a-e. For example, processors532 a-e may conjunctively determine how much power will be drawn by eachof loads 518 a-e such that all of the power produced by the solar arrayis consumed. Alternatively, or in addition, processors 532 a-e mayconjunctively determine how much power will be drawn by each of loads518 a-e such that a rate of change of power consumption by loads 51 8a-e does not exceed a threshold or maximum level of Watts per second oftime.

In a final step 312 (FIG. 3), if the DC loads cannot consume all of theelectrical output of the solar power device, then a remaining portion ofthe electrical output of the solar power device is converted into ACelectrical power. There may also be situations in which the load 418 a-nare capable, strictly speaking, of consuming all of the electricaloutput of the solar power device 412, but processor 424 does not allowone or more the loads 418 a-n to consume all the power they are capableof consuming in order to avoid damaging or overheating loads 418 a-n. Inthe above-described embodiment including loads in the form of airconditioning motors, processor 424 may not allow one or more the motorto consume all the power they are capable of consuming in order to avoidburning out the motors. Regardless of whether the loads are physicallyincapable of consuming all of the electrical output of the solar powerdevice or the processor prevents the loads from consuming all of theelectrical output of the solar power device strictly to avoid damagingthe loads, the remaining portion of the electrical output of solar array412 may be converted in AC electrical power. This AC electrical powermay then be consumed by AC appliances within the building, consumed byfull home, commercial building loads, or sent to the grid for use byother consumers.

Other features of electrical power supply arrangement 400 may besubstantially similar to those of electrical power supply arrangement100 as described above, and thus are not further described herein inorder to avoid needless repetition.

In FIG. 6 there is illustrated still another embodiment of an electricalpower supply arrangement 610 of the present invention including a solarPV array 612, and a DC power bus 614 electrically connecting array 612to a bidirectional inverter 616 associated with a DC load 618. Inverter616 may convert DC voltage from array 612 to a DC voltage level that isappropriate for use by DC load 618. A uni-directional (e.g., one-way)power connector 634 may couple DC load 618 to inverter 616. Connector634 may allow current to flow in only one direction (e.g., from inverter616 to load 618), and may prevent current from flowing from load 618 toinverter 616 if load 618 happens to function as a generator for a briefperiod. In one embodiment, connector 634 may be in the form of one ormore diodes (not shown). Thus, uni-directional connector 634 may preventpower from load 618 from damaging inverter 616.

Array 612 may include a DC-to-DC converter which may convert the DCvoltage output by the solar array to a voltage level suitable fortransmission on bus 614. Inverter 616 may also convert DC voltage fromarray 612 to an AC voltage that may be used through the remainder of ahouse 620 with which arrangement 610 is associated. Excess AC power thatcannot be used within house 620 may be provided to a grid 622 for useoutside of house 620. In one embodiment, DC voltage from array 612 maybe converted to AC voltage by inverter 616 only if HVAC system 618 (orother variable AC or DC loads) cannot consume all of the DC power fromarray 612. A uni-directional (e.g., one-way) power connector 636 maycouple array 612 to inverter 616. Connector 636 may allow current toflow in only one direction (e.g., from array 612 to inverter 616), andmay prevent current from flowing from inverter 616 to array 612. In oneembodiment, connector 636 may be in the form of one or more diodes (notshown). Thus, uni-directional connector 636 may prevent power frominverter 616 from damaging electronics associated with array 612.

As the invention may be applied to an HVAC system as the load, ifheating or cooling is not needed while the PV electrical output isavailable, the circulation fan could still run to provide air filteringfunctionality. Similarly, the compressor could run in a dehumidificationmode. Buildings can also be “overcooled” or “overheated” by a slightamount, reducing future energy demand. Thus, by use of these techniques,all of the electrical power produced by the PV may be consumed by theHVAC system.

As the invention may be applied to a freezer or refrigerator as theload, the motor speed of the freezer's compressor could be varied tomatch or completely consume the PV electrical output. Any excesselectrical output could be used to “overcool”, or further lower, thefreezer temperature beyond the temperature that would ordinarily becalled for. This allows the thermal energy stored in the freezer to berecovered at night (when there may be no PV electrical output), therebyenabling the freezer to draw a lower level of electrical power fromother sources.

As the invention may be applied to a heat pump or conventional electrichot water heater as the load, the load can be adjusted to match orcompletely consume the PV electrical output. Any excess PV electricaloutput may be used to “overheat” the water above the temperature thatwould ordinarily be called for. Thus, the need to draw power from othernon-PV sources during the day or at night is reduced.

As the invention may be applied to a water pump as the load, the pumpcould be run at variable speed to match or completely consume the PVoutput. Any extra water that is pumped at a higher motor speed may bestored or deployed during the daytime, thereby reducing the nighttimeneeds for pumping water.

As the invention may be applied to electric vehicle charging as theload, the battery charge rate can vary with PV electrical output. A DCpower bus between the PV system and the DC motor loads may provide anefficient way to vary the load. PV modules output DC voltage, soutilizing the DC voltage directly via the DC power bus withoutconversion to AC voltage may reduce conversion losses.

In one embodiment, a DC input Variable Frequency Drive (VFD) for an ACmotor or DC brushless motor provides an efficient way to vary the speedof a motor and thereby vary the load to match the PV electrical output.The DC input Variable Frequency Drive may be employed to vary the amountof work done instead of the conventionally-used on/off cycle or dutycycle. A DC input Variable Frequency Drive may be employed in an HVACsystem, an irrigation water pump, or a refrigerator, for example.

In one embodiment, the application is applied to HVAC systems oncommercial rooftops. Wiring costs and electrical losses may be reducedby directly feeding the PV power into the HVAC rooftop compressor or airhandling unit. Losses may be further reduced by utilizing a DC bus to aDC motor.

The principle of solar synchronized DC loads may be applied tostandardized DC building bus systems (e.g., the emerging 380 VDCstandard). In one embodiment, PV modules may contain DC/DC converters,with the known inherent benefits of ease of application, flexibility tomodify the system to accommodate rooftop changes, tolerance toshadowing, etc. Various building electrical loads may be developed tooperate off a standardized voltage (e.g. 380 VDC), and all loads may besynchronized to PV output via central control to minimize variation ingrid demand.

The invention may beneficially influence electricity consumption via asmart grid. For example, the peak power load and the peak powergeneration by the utility company may be reduced by the invention.

In another aspect, the invention may realize system synergies. Forexample, the invention may enable the coordination of run times, preventoverloading, and enable the scheduling of events based on the currentweather or forecast (e.g., the amount of cloud cover).

In another aspect, the communication between the solar array and theloads, and the potential communication between the various loads enabledby the invention may enable the homeowner/user/operator to locally andremotely control the user interface. For example, the user may controlthe user interface from his couch within the building, from his workplace remotely, or from his vacation home remotely. This local and/orremote user control may include reviewing performance data, schedulingoperation of appliances based on power cost rates, reviewing billing,and optimizing operation.

In another aspect, the invention may include features utilized by aprofessional appliance installer. For example, the installer may beprovided with an interface for remotely servicing, diagnosing, and/ortroubleshooting. This interface may eliminate the need for the installerto make a trip to the job site for troubleshooting. The interface mayalso enable the installer to offer system optimization as a service.

In still another aspect, the invention may enable an appliancemanufacturer to optimize the appliance or system remotely. The appliancemanufacturer may also remotely diagnose the appliance or system tothereby assist the installer. The invention may also enable theappliance manufacturer to monitor the performance of the appliance orsystem, as well as monitor the appliance or system on a long-term basis.

In a further aspect, the invention may provide a central user interfacein the form of an existing device that is already familiar to the user,such as an iPhone, television or laptop computer. By using a familiarinterface, the number of questions from the user is reduced, the numberof errors made by the user is reduced, and the user is enabled to havean intuitive interaction with the appliance.

In a still further aspect, the invention may operate with a universalopen source protocol, such as Zigbee, WLAN, etc. Thus, interaction withother devices may be enabled.

In another aspect of the invention, there may be a gateway with firewallin each appliance or device. Thus, a high level of operational securitymay be provided.

In yet another aspect, the invention may be integrated in a homenetwork. Such home networks may include the Google power meter or AppleApps, and/or may be marketed by the Microsoft HomeStore.

In a further aspect, the invention may include a parallel DC network toeliminate DC-to-AC conversion or AC-to-DC conversion. Thus significantlosses caused by such conversions may be eliminated.

The invention has been described in some embodiments above as applyingto an HVAC system. However, in other embodiments, the invention isapplied to domestic hot water (DHW), building access control/alarmsystems/security systems/fire alarms, automobile charging (electricvehicle/plug-in hybrid electric vehicle), kitchen appliances, media,internet, etc.

The invention has been described above as applying to a DC power sourcein the form of a solar array. However, in other embodiments, theinvention is applied to other sources of DC power, such as the rectifiedoutput of a wind turbine, for example. The invention may be applied toany DC power source, but may be particularly applicable to a DC powersource whose level of DC power output fluctuates with time.

In another embodiment, a bidirectional inverter, similar tobidirectional inverter 16 in FIG. 1, includes a DC solar variablefrequency drive (VFD) optimizer. This embodiment may be advantageouswith an electric vehicle charger or DC LED lighting being powered on thebus between the solar PV array and the DC VFD optimizer. The solar VFDoptimizer may remove the need for a solar inverter and may minimize ACcycling on the utility supply (e.g., demand smoothing).

With a variable frequency drive used in conjunction with an HVAC, thespeed of rotation may be driven by solar radiation. Also, there may belonger cycles if necessary to offset slower compressor rotation.Further, this variable frequency drive to HVAC embodiment may seekconstant draw from the utility as opposed to ON/OFF cycling.

The solar variable frequency drive (VFD) optimizer may enablepost-installation changes to the solar configuration, and may enable theuse of a high voltage DC power bus, such as could be used with LEDlighting and/or EV changing as mentioned above. Also, the solar variablefrequency drive (VFD) optimizer embodiment may apply to refrigeration,pumping, etc.

While this invention has been described as having an exemplary design,the present invention may be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles.

What is claimed is:
 1. An electrical power supply arrangementcomprising: a solar power device configured to convert sunlight into DCelectrical power; an adjustable DC load configured to run on the DCcurrent electrical power; and a controller coupled to each of theadjustable DC load, the controller being configured to: adjust the DCloads such that the DC loads consumes a maximum amount of the electricaloutput of the solar power device.